Poly-Rx, Neosporin (combination), Cortisporin (combination)
Evidence Grade A — Regulatory approved. 7061 published studies. 66 registered clinical trials.
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Polymyxin B is a close relative of colistin, used as a last-resort intravenous antibiotic for gram-negative infections resistant to virtually all other drugs. Outside of critical care, most people encounter polymyxin B as an ingredient in over-the-counter antibiotic creams like Neosporin and eye drops like Polytrim — where the tiny amounts applied topically pose no systemic toxicity concerns.
7,061 published studies: 3098 human, 1729 animal, 1289 in-vitro, 302 reviews
Polymyxin B is marketed as Poly-Rx (injection, approved approximately 1964) and is a component of numerous topical products including Neosporin, Cortisporin, and Polytrim. Intravenous polymyxin B and colistin are generally considered interchangeable for systemic infections.
Recent international consensus guidelines recommend targeting specific blood level thresholds for intravenous polymyxin B. Kidney injury rates are comparable to colistin (approximately 40–45%), but polymyxin B may cause more neurotoxicity (all reversible). Outside of critical care, the vast majority of polymyxin B use is in over-the-counter topical antibiotic combinations for minor skin wounds and eye infections, where systemic toxicity is not a concern.
Polymyxin B works through the same fundamental mechanism as colistin — binding to lipid A on the gram-negative bacterial outer membrane, disrupting membrane integrity, and causing cell death. The key pharmacological difference is that polymyxin B is given in its active form, while colistin is given as an inactive prodrug that must be converted in the body. This means polymyxin B reaches effective concentrations more rapidly and predictably, which matters in critically ill patients.
Like colistin, polymyxin B was approved decades before modern trial standards, so its evidence base consists largely of observational data from critically ill patients. Kidney injury occurs in approximately 40-45% of patients receiving intravenous polymyxin B — comparable to colistin — though it may cause more neurological side effects. The pharmacological advantage over colistin is that polymyxin B is administered in its active form, reaching effective blood levels more rapidly and predictably. Colistin is given as an inactive prodrug that must be converted in the body, introducing variability. For critically ill patients, this predictability matters. International guidelines now recommend specific blood level targets for intravenous polymyxin B. No large randomised trials have compared it against newer antibiotics.
Evaluating the Use of Polymyxin B Cartridge Hemoperfusion for Patients With Septic Shock and COVID 19
Treatment of Acyclovir-Resistant Mucocutaneous Herpes Simplex Disease in Patients With AIDS: Open Label Pilot Study of Topical Trifluridine
Open-label Evaluation of Polymyxin B Hemoperfusion for Septic Shock
Safety, Pharmacokinetics and Efficacy of BV100 Plus Low Dose Polymyxin B Plus Ceftazidime/Avibactam, or Plus Cefiderocol in Patients With Pulmonary and Extrapulmonary Infections Due to Carbapenem-resistant Acinetobacter Baumannii-calcoaceticus Complex
A Phase I Study Comparing the Safety, Pharmacokinetics and Renal Effects of VRP-034 and Marketed Polymyxin B in Healthy Volunteers
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